1. Field of the Invention
The present invention relates to an apparatus and a method for generating commands for executing an orientation action of an NC machine tool.
In the present application, the term orientation action is defined as an action for changing the orientation of a workpiece with reference to a tool or the orientation of a tool with reference to a workpiece.
2. Description of the Prior Arts
Until now, when a free-form surface was going to be machined using a five-axis machine tool, an NC program including an interpolation command for an linerotational axis of a tool holding unit and an interpolation command for a workpiece supporting table was first prepared by an automatic programming device together with interpolation commands for linear axes, and then the free-form surface was machined by applying this NC program to an NC control device of the five-axis machine tool.
The above-mentioned automatic programming device generated the interpolation commands for the linear axes and, at the same time, calculated an optimum vector for the surface at each machining point, where the tool came in contact with the surface, on the basis of the generated interpolation commands, and then generated the interpolation commands for the linerotational axis of the tool holding unit and the linerotational axis of the workpiece supporting table so that the tool was always oriented toward the optimum vector at the machining point. Thus the automatic programming device generated an NC program including the interpolation commands for the linear axes and the interpolation commands for the angular motion axes.
As a result, when the obtained NC program has been applied to the NC control device of the five-axis machine tool, the geometrical relationship between the tool and the workpiece surface during machining will exhibit the behavior as shown in FIG. 11 and shown in exaggerated form in FIG. 12. Both of FIG. 11 and FIG. 12 show the behavior in the Y-Z plane for convenience.